1. Field of the Invention
The present invention relates to a parallel resonance whirl antenna, and more particularly, to a parallel resonance antenna (or parallel resonance whishler antenna) capable of uniformly transferring an RF power of very high frequency (VHF) band.
2. Description of the Related Art
In semiconductor device manufacturing processes, processes using plasma are frequently performed. Dry etching, chemical vapor deposition (CVD) and sputtering are examples of such processes. In order to enhance the process efficiency, a process using a high density plasma (HDP) having an ion concentration of approximately 1xc3x971011xe2x88x922xc3x971012 ions/cm3 is frequently employed at the present. It is well known that this high density plasma can be obtained by inductively coupled plasma (ICP).
To obtain the aforementioned high density inductively coupled plasma, many applications using the parallel resonance antenna have been tried, but it is not easy to obtain a plasma having a uniform density. Especially, it is much more difficult to obtain such a uniform plasma in the VHF band. The VHF band corresponds to a frequency band between 20 MHz and 300 MHz.
Accordingly, it is a technical object of the invention to provide a parallel resonance antenna having a new structure and capable of uniformly transferring an RF power of the VHF band.
To accomplish the above object, there is provided a parallel resonance antenna comprising: a whirl antenna having a plurality of antenna units installed two-dimensionally and radially around a central point, each of the antenna units having a ground point at a predetermined position thereof, portions outside the ground points respectively being bent in a same direction, the antenna units having a same size and direction, angles between the antenna units at the central point being all the same; a central conductive line connected to the central point to be normal to the whirl antenna, for being supplied with an RF power; a metal plate installed over and apart from the whirl antenna, the metal plate being connected with end portions of the antenna units, and having a penetration hole through which the central conductive line passes without contacting with the metal plate; and a variable resonance capacitor installed in series between the central conductive line and the metal plate.
The antenna units are made of copper. Preferably, the bent portions of the antenna units have an arc shape with the central point as a center point, and an inner portion of the ground point has a convex shape in the bent direction.
Also, the central conductive line, the antenna units and the metal plate have vacant inner spaces such that a cooling water supplied through the central conductive line is discharged via the antenna unit and the metal plate to an outside, the central conductive line, the antenna units and the metal plate being connected with each other such that the inner spaces thereof communicate with each other, and a cooling water discharge hole being furnished near the penetration hole of the metal plate.
Preferably, the antenna unit placed inside the ground point is longer than the antenna unit placed outside the ground point, or the antenna unit placed inside the ground point is the same in length as the antenna unit placed outside the ground point.
The metal plate is directly connected with the antenna units, to have an upward convex shape. Also, the antenna may further comprise an external conductive line vertically installed with the whirl antenna at the ends of the antenna units, and the metal plate is connection-supported to have a flat shape. In the latter case, the central conductive line, the antenna units and the metal plate have vacant inner spaces such that a cooling water supplied through the central conductive line is discharged via the antenna unit and the metal plate to an outside, the central conductive line, the antenna units and the metal plate being connected with each other such that the inner spaces thereof communicate with each other, and a cooling water discharge hole being furnished near the penetration hole of the metal plate.